I have already decided to teach it Earthquake, Sacred Fire, and Roost.
You shouldn't give it any of those moves unless its mixed (has attack and special attack EVs). My Ho-Oh has Sky Attack because its a STAB move and it (Sky Attack) is really strong. I can see yours doesn't have a STAB Flying type move and Ho-Oh is bulky enough to survive so it can sacrifice the turn when its charging up.
(just in case you don't want to wait for Sky Attack just use the Power Herb)
Hope I helped.